Under reamer



c. H. SHARP 3,347,323

UNDER BEAMER 2 Sheecs--Sheetv 1 Oct. 17, 1967 Filed May 3, 1965 2. mw Addy/nm.

Oct. 17, H. SHARP Y vUNDER BEAMER Filed May I5, 1965 2 Sheets-Sheet 2 United States Patent O 3,347,323 UNDER REAMER Carl H. Sharp, 7240 E. Compton, Paramount, Calif. 90723 Filed May 3, 1965, Ser. No. 452,710 8 Claims. (Cl. 175-269) ABSTRACT OF THE DISCLOSURE A reamer tool including, an elongate, vertically extending tubular body, screw threads at the upper end of the body to releasably secure the body with the lower end of an elongate string of fluid conducting drill pipe, a plurality of elongate circumferentially spaced, radially outwardly opening slots extending longitudinally of the body, an elongate arm arranged within each slot to normally occur within the confines of the slot, means pivotally securing the upper end of theseveral arms to the body, an elongate roller cutter rotatably carried by and projecting `radially inwardly from the lower end of each arm to nor- Inally occur within the confines of the body and fluid pressure operated actuating means within the body and responsive to fluid pressure within the body and the related string of drill pipe and operable to pivot the arms radially outwardly and upwardly and to shift the cutters radially outwardly from within the confines of the body, each cutter having a plurality of longitudinally spaced annular ro'ws of circumferentially spaced radially outwardly projecting formation engaging teeth, the axial spacing of the rows of teeth and the circumferential spacing of the teeth of said rows of teeth on each cutter being arranged so that when the cutters are shifted outwardly and are rotated into engagement with and about an adjacent annular shoulder in an earth formation surrounding the reamer the teeth of each cutter engage the i formation between the tracks of Vthe teeth of the other cutters, and-each tooth engages the formation at the point spaced circumferentially from the points of contact by teeth on adjacent tracks, the lower sides of the cutters being radially inwardly andtdownwardly inclined relative to the longitudinal -axis of the construction when in their actuated position, whereby the inner rows of teeth on the cutters engage the surrounding formation on radial planes below and in advancel of the outer rows of teeth on the cutters, the teeth on the cutters have radially inwardly and downwardly disposed surfaces to direct and urge the formation reduced thereby radially inwardly, and fluid circulating means `to wash the cutters and the formation acted upon by the cutters, said fluid circulating means including a diffuser having a flat, central, upwardly disposed disc shaped. surface arranged below the cutters and a nozzle carried by the body abovethe diffuser to direct ajet of` circulating fluid downwardly onto the diffuser, said diffuser serving to direct said circulating fluid radially outwardly acrossthe surface ofthe formation being acted upon and between the cutter teeth.

This invention relates to a weld tool and is more particularly concerned with that type of well tool forenlargingthe bore hole in an oil well and commonly referred to as an under reamer.

In the course of drilling an oil well and preparatory to putting thewell into production, it is common practice to drill and establish a pilot hole, below or beyond the lower end of the casing previously arranged in the well bore and to subsequently introduce an under reamer secured to the lower end of a drill string, through the casing and into the pilot hole to enlarge the said pilot hole for subsequent reception of a perforated liner and other production equipment.

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The art of under reaming is extremely old and highly developed. In past years, many under reaming tools have been provided, which tools have met with varying degrees of success, but none of which has proven to be as effective, efficient and economical as the structure that applicant has invented and which is disclosed in the following specification.

The under reamer structures provided by the prior art have become more and more complicated as the art has developed, with the result that the ordinary under reamer in use today is a complicated mechanism which is costly to manufacturetand service and which is subject to failure due to its inherent complexity.

An object of my invention is to provide a novel under reamer construction involving a minimum number of parts, each of which is simple in design, easy and economical to manufacture and a reamer construction which is highly effective and dependable in operation and which is easy and economical to operate and maintain. I

When advancing an under reamer longitudinally in the pilot hole' provided therefor, an annular shelf or ledge is established in advance of the reamer, which shelf is reduced by the reamer as it is rotated and advanced in the hole. The ordinary reamer is provided with a plurality of circumferentially spaced, horizontally disposed, radially extending roller cutters carried by radially shiftable arms. The cutters are provided with a plurality of circumferentially spaced longitudinally extending teeth. The teeth of the ordinary 'roller cutters used in under reamers establish substantially uninterrupted varying engagement or contact on the annular shelf or ledge established in the formation, along radial lines relative to the central axis of the hole, as the rollers are rotated about said ledge. This kind or type of cutting action requires the teeth of the cutters to break and reduce the formation, the full radial extent of the ledge or shelf and requires the teeth to displace'the reduced formation laterally relative to the radial lines ofcontact which they es` tablished. That is, the reduced formation, in the case of the ordinary reamer cutter, must be displaced substantially circumferentially and in` directions where it is backed up and supported by adjacent, unreducedformation.

An object of this invention is to provide an under reamer of the general character referred to including a plurality of -circumferentially spaced, cone-shaped cutters arranged on radially inwardly and downwardly inclined axes and having a plurality of longitudinally spaced, annular rows of formation engaging teeth; whereby the formation establishing the annular shelf or shoulder is and along lines of limited longitudinal extent, throughout, the surface of said ledge or shelf and in such a manner that the formation is reduced a bit or a chunk at a ltime, from the inside portion to the outside portion of said ledge, as the reamer is advanced and rotated.

It is a further object of this invention to provide teeth on the cutter cones with radially outwardly and downwardly disposed surfaces Iwhich serve to urge the cuttings or reduced formation radially inwardly toward the pilot hole and in a direction where the cuttings are unsupported or backed 'by adjacent formation.

During the course of under reaming, circulating fluid is introduced into the well through the drill string and through the under reaming tool to flush the cuttings or reduced formation upwardly into and through the annulus about the tool and its related drill string. In the case of the ordinary or conventional under reaming tool, circulating uid is directed downwardly onto the cutters and/or on to the ledge or shelf in the formation established by the cutters, to keep the cutters and/or shelf clean. This practice tends to flush the cuttings downwardly onto the ledge and in the way of the cutters and/ or into the pilot hole where said cuttings interfere with the desired operation of the tools.

An object of my invention is to provide novel fluid circulating and/ or directing means which is such that circulating uid is directed radially outwardly and upwardly onto the underside of the cutters and upwardly and outwardly across the shelf or ledge established by the tool; whereby the cuttings are initially directed outwardly and upwardly onto the underside of the cutters and upwardly and outwardly across the shelf or ledge established by the tool; whereby the cuttings are initially directly outwardly and upwardly into the annulus about the tool and away from the cutters and the pilot hole.

The various objects and features of my invention will be fully understood from the following detailed description of a typical preferred form and application of my invention, throughout which description reference is made to the accompanying drawings, in which:

FIG. 1 is an elevational view of my new under reamer, showing it arranged in a weld structure in an unactuated position;

FIG. 2 is a view similar to FIG. 1 and showing my under reamer in an actuated position;

FIG. 3 is a detailed sectional view of my under reamer showing it in an unactuated position;

FIG. 4 is a detailed sectional view similar to FIG. 3 and showing the construction in an actuated position;

FIG. 5 is an enlarged, detailed sectional view of a portion of the construction shown in FIG. 4;

FIG. 6 is `a transverse sectional view taken as indicated by line 6--6 on FIG. 5;

FIG. 7 is a transverse sectional view taken as indicated by line 7 7 on FIG. 5;

FIG. 8 is a transverse sectional view taken as indicated by line 8-8 on FIG. 5;

FIG. 9 is a transverse sectional view taken as indicated by line 9-9 on FIG. 5;

FIG. 10 is a transverse sectional view taken as indicated by line 10-10 on FIG. 5;

FIG. 11 is a transverse sectional view taken as indicated by line 11-11 on FIG. 5;

FIG. 12 is a transverse sectional view taken as indicated by line 12-12 on FIG. 5; and,

FIG. 13 is a plan view showing the annular shoulder established by my reamer construction, about the pilot hole, with a pattern applied thereto to indicate a pattern which the cutter teeth of my new under reamer might establish.

The under reamer A provided by this invention includes an elongate vertically extending sub 10 with a centra flow passage 11, and upwardly opening, internally threaded box r12 at its upper end and an externally threaded pin 13 at its lower end. The box 12 cooperatively receives an externally threaded pin 14 on the lower end of `a fluid conducting drill string 15, which string is made up of a plurality of stands of drill pipe and the like, in accordance with common practice.

The tool A further includes an elongate, vertically extending, cylindrical body having upper and lower portions 21 and 22.

The upper portion 21 of the body is provided with an upwardly opening, internally threaded box 23 in which the pin 13 of the sub 10 is threadedly engaged and an elongate, horizontally extending cylinder bore 24 continuing downwardly from the bottom of the box and terminating at a flat, upwardly disposed bottom 25.

The lower portion 22 of the body 20 has a central cylindrical guide passage 26 of less diametric extent than the cylinder bore 24, extending longitudinally through said lower portion and communicating with the cylinder bore at the bottom thereof.

It will be apparent that the guide passage and the 4 bottom ofthe cylinder bore cooperate to define an annular, upwardly disposed spring seat.

The lower portion 22 of the body is further provided with a plurality (3) of circumferentially spaced, elongate, longitudinally extending cutter arrn receiving slots having upper portions 27 of limited circumferential extent and enlarged lower portions 28, which enlarged lower portions are adapted to receive cutters, as will hereinafter be described.

The slots open radially outwardly and communicate with the passage 26. The upper portions 27 of the slots have straight, parallel sides and are closed at their upper or top ends. The lower enlarged portions 28 of the slots open downwardly and in such a manner that the lower end portion of the lower section defines a plurality (3) of depending nger-like members X.

The lower portion of the body is provided with an annular stop ring 30 having a downwardly and radially inwardly tapered seat 31. The stop ring 30 is arranged in the guide passage 28 substantially midway between the upper and lower ends of the upper lportions 28 of the slots and is xed therein as by welding.

An elongate pilot P having a plurality (3) of longitudinally extending vanes 32, joined as by welding along the central longitudinal axis of the construction, is arranged in axial alignment below the lower end of the body. The upper ends 33 of the vanes are flat and horizontally disposed and have their radial outer end portions xed and intricately joined to the lower terminal ends of the linger-like portions X of the body, by welding. The vanes 32 are turned or twisted helically and their lower end portions are rounded downwardly and radially inwardly, as clearly illustrated in the drawings.

The pilot P is adapted to guide the tool when the tool is in operation, as will hereinafter be described.

An elongate, vertically extending mandrel 49 is arranged within the body 20 to shift longitudinally therein. The mandrel 40 has a piston head 41 at its upper end, which head is slidably engaged in the cylinder bore 24 in the upper portion 21 of the body. The mandrel further has a lower, elongate, cylindrical driver portion 42 depending from the piston head and slidably engaged in the guide passage 26 in the lower portion 22 of the body 20.

The upper piston head is provided with a plurality of longitudinally spaced, radially outwardly opening annular grooves 43 in which suitable O ring seals 44 are engaged and carried to seal between the piston and the cylinder bore.

The lower end portion of the driver portion 42 of the mandrel 40 is provided with a radially inwardly and downwardly tapered, annular, cam face 45, which cam face is adapted to act upon and shift cutter supporting arms 70, carried by the body, from an unactuated position to an actuated position as will hereinafter be described and to engage and seat in the stop ring 30, when the structure is in its fully actuated position, as clearly illustrated in FIG. 5 of the drawings.

The mandrel 40 is further provided with a central longitudinal flow passage 46 and an elongate fluid conducting extension 47 of reduced diametric extent. The extension 47 communicates with the ow passage and depends from the lower end of the mandrel. A suitable combination flow bean and nozzle 4S is engaged in the lower end of the extension 47 and is adapted to direct a jet of circulating fluid axially downwardly toward the top or upper end of the pilot P where it impinges upon a at, horizontally disposed round or disc-shaped diffuser 49. The diffuser 49 is established by depositing or building up a body or mass of hard material, such as tungsten carbide, as by welding, at and `about the junction of the upper ends 33 of the several veins 32 and subsequently grinding a at, central, round or disc-shaped, upwardly'disposed surface thereon.

It will be apparent that when a jet of circulating uid impinges upon the diluser 49, the fluid is caused to spray and/or fan out, radially, through 360 degrees, at the lower end of the body.

A flow tube 50 is arranged in the upper end of the cylinder bore 24 in the upper portion 21 of the body 20. The tube 5t) communicates with the flow passage 11 in the sub and extends longitudinally downwardly through the cylinder bore into the flow passage 46 in the mandrel. The tube 50 establishes free running clearance in the said flow passage in the mandrel.

The upper end of the flow tube 50 is provided with a cylindrical enlargement or mounting head 51 which slidably enters the upper end of the cylinder bore. The mounting head 51 is held in fixed position in the bore by sutiable screw fasteners 52 carried by the body and engaged in said head. The head is further provided with an annular radially outwardly opening groove 52, below the fasteners, to receive and carry an O-ring 53 to seal between the head and the cylinder bore. The head 51 is further provided with an annular upwardly opening groove 55 in its upper end and in which an O ring 56 is engaged to seal between the top of the mounting head .and the lower end of the pin 13 of the sub 10, which pin seats and stops on the top of the head.

The flow tube Si) serves to direct fluid downwardly through the cylinder bore in such a manner as to prevent sand and other foreign matter carried by the circulating uid from building up on and above the top of the piston head 41 on the mandrel and in such a manner as might foul the construction and interfere with its proper operation.

The clearance between the ow tube 50 and the flow passage 46 in the mandrel is sufficient to allow or permit uid owing through the construction to enter the chamber or space between the piston head and the mounting head.

A suitable compression spring 60 is arranged in the annulus between the mandrel 40 and the cylinder bore, below the piston head and seats on the bottom 25 of the cylinder bore and the bottom or underside of the piston head, as clearly illustrated in the drawings. The spring 60 normally yieldingly urges the mandrel upwardly in the body to its unactuated position, `as illustrated in FIG. 3 of the drawings.

It will be apparent that the effective cross-sectional area of the mandrel and/ or piston extends radially from the outside diameter of the piston head 41 to the inside diameter of the opening or bore 61 of the nozzle 48, at the lower end of the extension 47 on the mandrel.

The roller cutter supporting arms 70 that I provide are elongate, normally vertically extending arms slidably engaged in the slots 27 in the body, each having its upper end pivotally mounted in the upper end of its related slot by a suitable pivot pin 71 carried by the body, as clearly illustrated in FIGS. 5 and 9 of the drawings.

Each arm 70 has a straight, upper portion which is coextensive with the upper portion 27 of its related slot and has an enlarged plate-like lower portion which normally occurs in the enlarged lower portion 28 of its related slot and on which a roller cutter 80 is rotatably supported.

The radially outwardly disposed sides of the arms 70 are suitably rounded or radiused and are related to the slots so that the said outer sides or surfaces are liush with the exterior of the body when the construction is in its unactuated position. i

Each arm 70 is provided with a radially inwardly projecting lug 72, which lug normally projects radially inwardly into the guide passage 26 of the body above the stop ring 30 and below the cam face 45 on the mandrel.

When the mandrel 40 is urged downwardly, the cam face 45 engages the lugs 72 lon the several arms and urges them radially outwardly with resulting radial outward and upward pivoting of the arms.

In practice, the inner ends of the lugs 72 are suitably radiused or formed so that proper bearing contact be- 6 tween the lugs and the cam face 45 is maintained throughout relative shifting between said parts.

The stop ring 30 is positioned in the body so that the cam face 45 on the lower end of the mandrel 40 seats and stops on the ring when the lugs reach the upper end of the cam face 45 and before the lugs shift above said cam face where they would effect a lock and prevent subsequent radial inward shifting of the lugs and arms.

Accordingly, the arms are held out by the hydraulic forces exerted through the construction and are not mechanically locked in their out or actuated position and in such a manner as might prevent shifting of the construction from its actuated position back to its unactuated position.

In addition to the foregoing and where circumstances require, secondary guide lugs 73 can be provided on the arms 70 to occur below the ring 30 in the body, which lugs remain engaged in the slots 27 when the construction is in its actuated position and effectively prevent the arms from being torqued and bent out of alignment upon rotation of the construction when the construction is making hole.

The lower portion of each arm is provided with a radially inwardly and downwardly inclined, cylindrical trunnion 75 on which the roller cutters 80 are rotatably mounted.

The roller cutters `are elongate, substantially cupshaped, conical members engaged about the trunnions 35 and rotatably coupled thereto by means of suitable antifriction bearings 81 and 82, as clearly illustrated in FIG. 5 of the drawings.

The cutters are provided with a plurality of axially spaced, annular rows of circumferentially spaced, radially outwardly projecting formation engaging teeth 83. The number and axial placement of the rows of teeth and/ or the number and circumferential spacing of the teeth of each row of teeth on the several cutters is such that when the cutters are in operation and are advanced into cutting or reducing engagement with a formation and the construction is rotated so as to cause the cutters to roll relative to the formation, the several teeth engage and act upon the formation at different points and do not follow in common tracks.

In FIG. 13 of the drawings, I have diagrammatically indicated a typical pattern established by my cutter teeth on a formation section.

In practice, each tooth has a substantially radially inwardly and downwardly disposed surface or end 84, which surface or end tends to urge the formation reduced or broken away from the surrounding or adjacent formation by the tooth, radially inwardly and toward the pilot hole 90, provided in the formation for the tool, where it is unsupported or backed up by solid or continuous adjacent formation.

In the preferred carrying out of the invention, the cutters are arranged at such an angle that when the tool is in its unactuated position, the innermost row of teeth occur on a horizontal plane below and cut in advance of the next, outer row or rows of teeth. Accordingly, the innermost portion of the formation, which is more easily broken and reduced, as a result of the presence of the pilot hole 90, is acted upon first and in advance of the remainder of the portion of the formation to be acted upon. As a result of the above, the tool reduces the formation progressively from the center outwardly, as it is advanced longitudinally downwardly.

The `cutters 80 are of such axial and diametric extent and the teeth thereon are so arranged that when the construction is in its unactuated position, the cutters enter and occur wholly within the lower portion 28 of their related notches in the body and their inner ends or tips and the cutter teeth thereon suitably nest together, as illustrated generally in FIG. 3 ofthe drawings.

When the construction is in its actuated position, 'as illustrated in FIGS. 4, 5 and 9 of the drawings, the outer ends of the teeth at the outer ends of the cutters and occurring at the lower sides of the cutters, occur radially outward of the lower ends of their related arms, whereby the arms do not interfere with the operation of the construction as by engaging and dragging on the sides of the bore hole established by the cutters.

In operation, the pilot hole 90 is established in a formation F below the shoe 100 at the lower end of a casing 101 set in a weld bore 102. The tool A, in its unactuated position and engaged on the lower end of the drill string is then lowered from the top of the weld structure, downwardly through the casing and into the pilot hole.

When thus arranged, circulating fluid, under considerable pressure, is flowed downwardly through the construction and through the combination flow bean and nozzle 48. The pressure of the fluid acts upon the piston 41 and urges the mandrel 40 downwardly against the resistance of the spring 60. Downward shifting of the mandrel urges the arms and cutters radially outwardly. The tool is then rotated to cut and open the pilot hole to full bore and is then advanced downwardly, while still being rotated, to complete the desired under reaming operation.

When the operation is completed, the fluid pressure is reduced and the spring 60 urges the mandrel back, upwardly in the body and the arms and cutters are free to swing downwardly and inwardly or back to their unactuated position. The tool is then removed from the weld structure.

In the event that the arms do not swing back into their unactuated position freely, drawing the tool upwardly through the shoe 100 at the lower end of the casing 101 urges the arms and cutters radially inwardly to their unactuated position. This is possible due to the fact that the arms are not locked in their out or actuated position by positive mechanical means.

It is very important and it is to be noted that the diffuser 49 occurs on a common plane with the lowermost teeth of the cutter so that the spray or fan of circulating fluid established thereby is directed radially outwardly across the surface of the formation being acted upon and between the teeth. The circulating fluid, therefore, initially flushes the cuttings radially outwardly where they are more readily picked up by the circulating fluid and carried directly into and upwardly through the annulus between the tool and the surrounding well structure.

Having described only a typical preferred form and application of my invention, I do not wish to be limited to the specific details herein set forth, but wish to reserve to myself any modifications and variations that may appear to those skilled in the art and which fall within the scope of the following claims.

Having described my invention I claim:

1. An under reamer of the character referred to including, an elongate vertically extending tubular body, screw threads at the upper end of the body to releasably secure the body with the lower end of an elongate string of fluid conducting drill pipe, a plurality of elongate circumferentially spaced, radially outwardly opening slots extending longitudinally of the body, an elongate arm arranged within each slot to normally occur within the contines of the slot, means pivotally securing the upper end of the several arms to the body, an elongate roller cutter rotatably carried by and projecting radially inwardly from the lower end of each arm to normally occur within the confines of the body and fluid pressure operated actuating means within the body and responsive to fluid pressure within the body and the related string of drill pipe and operable to pivot the arms radially outwardly and upwardly and to shift the cutters radially outwardly from within the conflnes of the body, each cutter having a plurality of longitudinally spaced annular rows of circumferentially spaced radially outwardly projecting formation engaging teeth, the axial spacing of the rows of teeth and the circumferential spacing of the teeth of said rows of teeth on each cutter being arranged so that when the cutters are shifted outwardly and are rotated into engagement with and about an adjacent annular shoulder in an earth formation surrounding the reamer, the teeth of each cutter engage the formation between the tracks of the teeth of the other cutters and each tooth engages the formation at a point spaced circumferentially from the points of contact by teeth on adjacent tracks.

2. A structure as set forth in claim 1 wherein the teeth on the cutters have radially inwardly and downwardly disposed surfaces to direct and urge the formation reduced thereby radially inwardly.

3. A structure as set forth in claim 1 including fluid circulating means to wash the cuttings and the formation acted upon by the cutters, said fluid circuating means including a diffuser having a flat, central, upwardly disposed disc shaped surface arranged below the cutters and a nozzle carried by the body above the diffuser to direct a jet of circulating fluid downwardly onto the diffuser, said diffuser serving to direct said circulating fluid radially outwardly across the surface of the formation being acted upon and between the cutter teeth.

4. A structure as set forth in claim 1 wherein said fluid pressure actuating means includes an elongate upwardly opening axially extending cylinder bore in the body above the slots ltherein and communicating with the fluid conducting drill string and terminating at a flat bottom, a central guide passage `continuing downwardly through the lbody from the bottom of the cylinder bore and communicating with the slots therein, an elongate mandrel with a central longitudinal flow passage arranged in the guide passage and extending upwardly into the cylinder bore and having an enlarged cylinder bore engaging piston at its upper end and a radially inwardly and downwardly convergent annular cam face at its lower end, an elongate flow tube mounted in the upper end of the cylinder bore to depend freely therethrough and into the flow passage and to conduct the primary flow of circulating fluid from the drill string through the cylinder bore and into the fluid passage, a radially inwardly projecting cam face engaging lug on each arm below its upper end to normally project freely into the guide passage below the cam face and to be engaged and urged radially outwardly by the cam face upon downward shifting of the mandrel in the body, a compression spring between the bottom of the piston and the bottom of the cylinder bore to normally yieldingly urge the mandrel upwardly in the body, an annular stop ring in the guide passage below the mandrel to engage and stop the mandrel when it is urged downwardly and reaches its fully actuated position, and a flow bean at the lower end of the flow passage to restrict the flow of circulating fluid through the construction and to control the effective cross-sectional area of the piston and mandrel.

5. A structure as set forth in claim 1 wherein said fluid pressure actuating means includes an elongate upwardly opening axially extending cylinder bore in the body above the slots therein and communicating with the fluid conducting drill string and terminating at a flat bottom, a central guide passage continuing downwardly through the body from the bottom of the cylinder bore and cornmunicating with the slots therein, an elongate mandrel with a central longitudinal flow passage arranged in the guide passage and extending upwardly into the cylinder bore and having an enlarged cylinder bore engaging piston at its upper end and a radially inwardly and downwardly convergent annular cam face at its lower end, an elongate flow tube mounted in the upper end of the cylinder bore to depend freely therethrough and into the flow passage and to conduct the primary flow of circulating fluid from the drill string through the cylinder bore and into the fluid passage, a radially inwardly projecting cam face engaging lug on each arm below its upper end to normally project freely into the guide passage below the cam face and to `be engaged and urged radially outwardly by the cam face upon downward 9 shifting of the mandrel in the body, a compression spring between the bottom of the piston and the bottom of the cylinder bore to normally yieldingly urge the mandrel upwardly in the body, an annular stop ring in the guide passage below the mandrel to engage and stop the mandrel when it is urged downwardly and reaches its fully actuated position, and a llow bean at the lower end of the ow passage to restrict the flow of circulating fluid through the construction and to control the effective cross-sectional area of the piston and mandrel, said How bean directing a jet of circulating fluid downwardly onto a diffuser arranged centrally of the body and below the cutters, said diffuser having a ilat upwardly disposed disc shaped surface to direct the jet of circuating fluid radially outwardly below the cutters and between the teeth thereon.

6. An under reamer of the character referred to including, an elongate vertically extending tubular body, screw threads at the upper end of the body `to releasably secure the body with the lower end of an elongate string of fluid conducting drill pipe, a plurality of elongate circurnferentially spaced, radially outwardly opening slots extending longitudinally of -the body, an elongate arm arranged within each slot to normally occur within the contines of the slot, means pivotally securing the upper end of the several arms to the body, an elongate roller cutter rotatably carried by and projecting radially inwardly from the lower end of each arm to normally occur within the lcontines of the body and fluid pressure operated actuating means within the body and responsive to fluid pressure within the body and the related string of drill pipe and operable to -pivot the arms radially outwardly and upwardly and to shift the cutters radially outwardly from Within the contines of ythe body, each cutter having a plurality of longitudinally spaced annular rows of circumferentially spaced radially outwardly projecting formation engaging teeth, the axial spacing of the rows of teeth and the circumferential spacing of the teeth of said rows of teeth on each cutter being arranged so that when the cutters are shifted outwardly and are rotated into engagement with and about an adjacent annular shoulder in an earth formation surrounding the reamer -the teeth of each cutter engage the formation between the tracks of the teeth of the other cutters and each tooth engages the formation at a point spaced circumferentially from the points of contact by teeth on adjacent tracks, the lower sides of the cutters 'being'radially inwardly and downwardly inclined relative to the longitudinal axis of the construction when in their actuated position, whereby the inner rows of teeth on the cutters engage the surrounding formation on radial planes below and in advance of the outer rows of teeth on the cutters.

7. A structure as set forth in claim 6 wherein the teeth 0n the cutters have radially inwardly and downwardly disposed surfaces to direct and urge the formation reduced thereby radially inwardly.

8. A structure as set forth in claim 6 wherein the teeth on the cutters have radially inwardly and downwardly disposed surfaces to direct and urge the formation reduced thereby radially inwardly, and fluid circulating means to wash the cutters and the formation acted upon by the cutters, said fluid circuating means including a diffuser having a flat, central, upwardly disposed disc shaped surface arranged below the cutters and a nozzle carried by the body above the diffuser to direct a jet of circulating fluid downwardly onto the diuser, said diffuser serving to direct said circuating fluid radially outwardly across the surface of the formation being acted upon and between the cutter teeth.

References Cited UNITED STATES PATENTS 2,527,838 10/1950 Morlan et al 175-376 2,545,036 3/ 1951 Kammerer 175--271 2,805,045 9/1957 Goodwin 175-341 X 2,887,302 5/1959 Garner 175-376 X 3,123,160 3/1964 Kammerer 175-269 X 3,126,065 3/ 1964 Chadderson 175-269 3,283,834 1l/1966 Kammerer 175-26-7 CHARLES E. OCONNELL, Primary Examiner. R. E. FAVREAU, Assistant Examiner. 

1. AN UNDER REAMER OF THE CHARACTER REFERRED TO INCLUDING, AN ELONGATE VERTICALLY EXTENDING TUBULAR BODY, SCREW THREADS AT THE UPPER END OF THE BODY TO RELEASABLY SECURE THE BODY WITH THE LOWER END OF AN ELONGATE STRING OF FLUID CONDUCTING DRILL PIPE, A PLURALITY OF ELONGATE CIRCUMFERENTIALLY SPACED, RADIALLY OUTWARDLY OPENING SLOTS EXTENDING LONGITUDINALLY OF THE BODY, AN ELONGATE ARM ARRANGED WITHIN EACH SLOT TO NORMALLY OCCUR WITHIN THE CONFINES OF THE SLOT, MEANS PIVOTALLY SECURING THE UPPER END OF THE SEVERAL ARMS TO THE BODY, AN ELONGATE ROLLER CUTTER ROTATABLY CARRIED BY AND PROJECTING RADIALLY INWARDLY FROM THE LOWER END OF EACH ARM TO NORMALLY OCCUR WITHIN THE CONFINES OF THE BODY AND FLUID PRESSURE OPERATED ACTUATING MEANS WITHIN THE BODY AND RESPONSIVE TO FLUID PRESSURE WITHIN THE BODY AND THE RELATED STRING OF DRILL PIPE AND OPERABLE TO PIVOT THE ARMS RADIALLY OUTWARDLY AND UPWARDLY AND SO TO SHIFT THE CUTTERS RADIALLY OUTWARDLY FROM WITHIN THE CONFINES OF THE BODY, EACH CUTTER HAVING A PLURALITY OF LONGITUDINALLY SPACED ANNULAR ROWS OF CIRCUMFERENTIALLY SPACED RADIALLY OUTWARDLY PROJECTING FORMATION ENGAGING TEETH, THE AXIAL SPACING OF THE ROWS OF TEETH AND THE CIRCUMFERENTIAL SPACING OF THE TEETH OF SAID ROWS OF TEETH ON EACH CUTTER BEING ARRANGED SO THAT WHEN THE CUTTERS ARE SHIFTED OUTWARDLY AND ARE ROTATED INTO ENGAGEMENT WITH AND ABOUT AN ADJACENT ANNULAR SHOULDER IN AN EARTH FORMATION SURROUNDING THE REAMER, THE TEETH OF EACH CUTTER ENGAGE THE FORMATION BETWEEN THE TRACKS OF THE TEETH OF THE OUTER CUTTERS AND EACH TOOTH ENGAGES THE FORMATION AT A POINT SPACED CIRCUMFERENTIALLY FROM THE POINTS OF CONTACT BY TEETH ON ADJACENT TRACKS. 